The present invention relates to a zoom lens barrel and a camera employing the zoom lens barrel, and more particularly, to a zoom lens barrel having therein a zooming region and an accommodating region and to a camera such as a digital camera and a video camera employing this zoom lens barrel.
As a zoom lens barrel, there has so far been a barrel which conducts a change of a focal length of a lens system and an accommodating action. For example, FIG. 6 shows constitution for a change of a focal length and an accommodating action in a zoom lens barrel representing an example of a prior art. As shown in the diagram, cam member 151 is provided with cam grooves 152 and 153. The cam groove 152 is engaged with pin 172 which is provided on lens supporting frame 171 having therein lens group 173, and the cam groove 153 is engaged with pin 182 which is provided on lens supporting frame 181 having therein lens group 183.
The pins 172 and 182 are engaged also with linear guide groove 161, and when the cam member 151 is turned in the direction of arrow mark A, the lens supporting frames 171 and 181 are guided by the linear groove 161 representing a guide member to move in the direction of arrow mark B. The cam grooves 152 and 153 make zooming action to be conducted by the portions of position P1 and position P2, and make accommodating action to be conducted by the portions of position P2 and position P3 (TOKKAIHEI No. 2-6914).
However, since each of the cam grooves 152 and 153 on the cam member 151 has a groove portion for zooming and a groove portion for accommodating, the cam grooves 152 and 153 are long in the direction which is in parallel with an optical axis. In particular, for those wherein an optical system such as CCD is required to have telecentric characteristics in an image pickup element, the position of a lens in the course of photographing is far from CCD in the direction which is in parallel with an optical axis in many cases. Therefore, an amount of movement for accommodating is large, and thereby, cam grooves 152 and 153 are long in the direction being in parallel with an optical axis, which is a problem. Further, in the high magnification zoom lens wherein a lens group moves in full measure in the direction being in parallel with an optical axis between the occasion of accommodating and that of photographing, in particular, cam grooves 152 and 153 are long in the direction being in parallel with an optical axis, and a total length in the case of accommodating is long, which is a problem.
To prevent an error of lens inclination to an optical axis of an optical system, it is usually preferable to arrange three cam grooves. However, when the cam grooves are long as stated above, a diameter of a cam member is increased and a rise angle of the cam groove is made to be steep, for providing three cam grooves without an interference, which causes a problem that load on the driving section is increased.
The invention has been achieved in view of the problems stated above, and one of objects of the invention is to provide a zoom lens barrel which can easily be applied to a camera excellent in portability, by making a zoom lens which causes a camera to be large in size to be accommodated easily in a camera main body. Another object of the invention is to provide a camera to which the barrel stated above is applied.
The objects mentioned above are attained by either one of the following structures.
(1) A camera having a zooming function wherein there are provided a plurality of lens groups, a fixed frame fixed to a main body of the camera, a cam member engaging with the fixed frame so that the cam member is moveable in the optical axis direction, and a plurality of lens group supporting frames each engaging with the cam member and supporting each of the plural lens groups so that the lens group supporting frames may move in the optical axis direction to move the lens groups in the optical axis direction.
Due to this structure, even in the case of a camera wherein an amount of movement of lens groups is large, such as a digital camera and a video camera, cam grooves provided on a cam member can be made short in the optical axis direction, and a camera can be made small in size, because not only lens group supporting frames but also the cam member and lens group supporting frames are protruded in the optical axis direction when protruding the zoom lens barrel from a camera main body.
(2) A zoom lens barrel wherein there are provided a plurality of lens groups, a plurality of lens group supporting frames each supporting each of the plural lens groups, a guide member which guides plural lens group supporting frames in the direction being in parallel with an optical axis, a cam member which moves plural lens group supporting frames in the direction being in parallel with an optical axis by the movement of the lens group in the direction being in parallel with an optical axis, and moves at least two lens supporting frames among plural lens group supporting frames by the rotation of the lens group around an optical axis, a fixed frame which is composed of a first guide portion which guides the cam member in the direction being in parallel with the optical axis and of a second guide portion which guides the cam member in the direction to rotate around the optical axis, and a driving member which drives the cam member.
(3) The zoom lens barrel described in the above item (2) wherein the first guide portion and the second guide portion both formed on the fixed frame mentioned above are continuous cam grooves engaging respectively with the cam member,
(4) The zoom lens barrel described in the above item (3) wherein the first guide portion is a cam groove formed continuously in the direction for moving the cam member in the optical axis direction, and the second guide portion is a cam groove formed continuously in the direction for rotating the cam member without moving it substantially in the direction being in parallel with an optical axis.
(5) The zoom lens barrel described in the above item (4) wherein the cam groove of the first guide portion is a cam groove formed continuously in the direction which is mostly in parallel with an optical axis, and the cam groove of the second guide portion is a cam groove
(6) The zoom lens barrel described in Item (3) wherein the first guide portion is a cam groove formed continuously in the direction for moving the cam member in the direction parallel to the optical axis direction and for rotating, and the second guide portion is a cam groove formed continuously in the direction for rotating the cam member without moving it substantially in the direction being in parallel with an optical axis.
(7) The zoom lens barrel described in Item (6) wherein a cam groove of the first guide portion is one formed continuously in the direction inclined to the optical axis, and a cam groove of the second guide portion is one formed continuously in the prescribed direction in the plane which is mostly perpendicular to the optical axis.
(8) The zoom lens barrel described in either one of Item (2)-Item (7) wherein the driving member is a rotating ring having a cam groove which engages with the cam member for transmitting driving force to the cam member.
(9) The zoom lens barrel described in Item (8) wherein a cam groove of the rotating ring is one which is formed continuously in the direction inclined to the optical axis for moving the cam member in the optical axis direction and for rotating it.
(10) The zoom lens barrel described in Item (8) wherein a cam groove of the rotating ring is one wherein a portion formed continuously in the direction inclined to an optical axis for the purpose of moving the cam member in the optical axis direction and a portion formed continuously in the optical axis direction for the purpose of rotating the cam member without moving it substantially in the optical axis direction are connected.
(11) The zoom lens barrel described in Item (7) wherein the driving member is a rotating ring having a cam groove which is formed continuously in the optical axis direction and engages with the cam member to transmit driving force to the cam member.
(12) The zoom lens barrel described in either one of Items (2)-(11), wherein the guide member has a straight guide portion for guiding straight in the direction which is almost in parallel with an optical axis.
(13) The zoom lens barrel described in either one of Items (2)-(12), wherein the plural lens group is a zoom lens composed of two lens groups.
(14) A camera having a zoom lens barrel described in either one of Items (2)-(13).
(15) A zoom lens barrel wherein there are provided a plurality of lens groups, a plurality of lens group supporting frames which respectively support the plural lens groups, a guide member which guides straight the plural lens group supporting frames in the optical axis direction, a cam member which moves the plural lens group supporting frames in the optical axis direction by the movement in the optical axis direction and moves at least two lens supporting frames among the plural lens group supporting frames in the optical axis direction by the rotation, a fixed frame fixed on a camera main body representing a cam groove which engages with a pin provided on the cam member and is composed of a first guide portion which guides the cam member in the optical axis direction and of a second guide portion which is connected with the first guide portion which guides the cam member around the optical axis, and a rotating ring having a cam groove which is provided with a portion which engages with the pin through the cam groove provided on the fixed frame and is formed continuously in the direction inclined to the direction of the optical axis provided to face the first guide portion for the purpose of moving the cam member in the optical axis direction and with a portion provided to face the second guide portion for the purpose of rotating the cam member without moving it substantially in the optical axis direction.
(16) A camera capable of being in the accommodated state in which a zoom lens barrel having therein plural lens groups is accommodated in the camera main body and in the state of ready for photographing in which the zoom lens barrel is protruded in the direction being in parallel with an optical axis, wherein there are provided a cam member which shifts the zoom lens barrel from the accommodated state to the state of ready for photographing, or from the state of ready for photographing to the accommodated state by the movement in the optical axis direction, and moves at least two lens groups in the optical axis direction so that they draw a prescribed locus by the rotation when the zoom lens barrel is in the state of ready for photographing, thereby to conduct prescribed zooming, and a fixed frame having a guide member which engages with the cam member and guides the movement of the cam member in the optical axis direction.